Magnetic concentration apparatus



Nov. 19, 1963 D. A. CAVANAGH MAGNETIC CONCENTRATION APPARATUS 4Sheets-Sheet 1 Onginal Filed Jan. 5, 1953 FIG! PICKUP TRANSFER DISCHARGEIS //9 l \fi 20 0A 8 POWER TO LAST THREE co/zs FIG. 2

FIG.3

CLASSH CLASS I CONCENTRATE FIG.6

Inventor DANIEL A. CAVANAGH Nov. 19, 1963 D. A. CAVANAGH 3,111,484

MAGNETIC CONCENTRATION APPARATUS orlginal Filed Jan. 5; 1953 4Sheets-Sheet 2 Inventor DANIEL A. CAVANAGH Nov. 19, 1963 D. A. CAVANAGHMAGNETIC CONCENTRATION APPARATUS Onginal Filed Jam. 5, 1953 4Sheets-Sheet 3 ,6 FIG. 7

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FIG. 10

Inventor DANIEL A. CAVANAGH Nov. 19, 1963 D. A. CAVANAGH 3,111,484

MAGNETIC CONCENTRATION APPARATUS Onginal Filed Jan. 5, 1953 9 4Sheets-Sheet 4 66 FIG. 8

6i s A as 8 a 96 9/ 86 a9 v 88 W \lTzzj 4 i I i /\9$ hzmfl I F I G. 11

Inventor DANIEL A. CAVANAGH United States Patent ()fiice 3,113,484Patented Nov. 19%, 1963 3,111,484 MAGNETIC CONCENTRATIQN APPARATUSDaniel Alfred Cavanagh, Warren, Qhio (43 Owen Blvd, Willowdaie, Gntario,Canada) Original application Jan. 5, 1953, Ser. No. 329,657, new PatentNo. 3,045,821, dated .Iuly 24, 1962. Divided and this application Oct.13, 1958, Ser. No. 767,030

18 Claims. (Cl. 20227) This invention relates to apparatus forseparating magnetic particles from finely divided material and moreparticularly to improvements in concentration apparatus for thepolyphase travelling field class of magnetic separation. Thisapplication is a division of application Serial No. 329,657, now PatentNo. 3,045,821, granted July 24, 1962.

It is known that prior polyphase travelling field ma netic separatorsare seriously limited in capacity. The flux density which can bedeveloped for the purpose of providing a travelling field in themagnetic core construction of prior apparatus is limited to an extentmaking such devices impractical for many applications. In such priorapparatus, a large number of poles have been provided in the corestructure of the device in order to accomplish separation efiiciency, byarranging a large plurality of such poles equidistant from and close toa conveying device for the materials being separated. Thecharacteristics of such devices of the analogous prior art are outlinedin a paper titled Three-Phase A. C. Can Improve Fine-Size MagneticSeparation, published in Engineering and Mining Journal of October 1951by McGraw-Hill Publishing Company of New York. According to theestablished art, the desired separation effect has been accomplishedmainly by providing a large number of poles numbering seventy-two ormore.

It is a main object of the present invention to provide a polyphasetravelling field magnetic separator of a relatively small number ofpoles comprising pickup and discharge groups.

Another object of the invention is to provide a sloped mounting of atravelling field magnetic separator with respect to the finely dividedmaterial conveyor or feeder therefor whereby the major separation effectpractised upon the material is accomplished in the step of lifting thematerial from the conveyor.

A further object of the invention is to provide an improved constructionof travelling field magnetic separator embodying a winding assemblywherein the windings are directly cooled.

A still further object of the invention is to provide improvements inpolyphase magnetic separators wherein the physical size of the poles andthe spaces therebetween, are unlimited except by the largest size ofmagnetic material desired to be handled and the properties of the corematerial.

A still further object of the invention is to provide a cleaning of theconcentrate obtained by a travelling field magnetic separator by the useof an air stream.

A still further object of the invention is to provide an automaticdischarge device operative by the removal of a portion of the magneticfield from a portion of the core of the separator.

A still further object of the invention is to provide a cover sheet forthe core, of a magnetic material specifically for the purpose of shapingthe field generated from the poles in contrast to prior practice ofemploying nonmagnetic materials for such a cover sheet.

A still further object of the invention is to provide a field shapingcore associated with the core of the separator in such manner that theconveyor or feeder device passes therebetween.

It is a still further object of the invention to provide a travellingfield magnetic separator of high intensity operative upon weaklymagnetic materials.

Other objects of the invention will be appreciated by a study of thefollowing detailed specification taken in conjunction with theaccompanying drawings.

In the drawings:

FIGURE 1 is a diagrammatic view of the core arrangement of a polyphasetravelling field magnetic separator device illustrating pickup, transferand discharge sections thereof;

FIGURE 2 is an electrical schematic laid over a plan view of a polediagram of the core of FIGURE 1, illustrating the preferred type ofwinding for such core according to the invention for two active sectionssuch as a pickup section and a transfer section;

FIGURE 3 is an electrical schematic of a system according to theinvention for providing discharge of material from the magneticseparator device;

FIGURE 4 is a diagrammatic view of actuating means for the dischargeelectrical apparatus of FIGURE 3;

FIGURE 5 illustrates a manner of modulating the current in the windingsof the discharge section of the separator with the device of FIGURE 4 inconjunction with the electrical schematic of FIGURE 3;

FIGURE 6 is a diagrammatic view of the device of the invention,including an electrical schematic of the manher in which separation ofmaterials may be controlled by controlling the voltage of the windinggroups of the separator core;

FIGURE 7 is a partial sectional view of the core construction for apolyphase travelling field magnetic separator according to theinvention, particularly illustrating a method of directly cooling thewindings thereof and also illustrating a preferred manner of disposingthe separator with respect to a conveyor for material being fed thereto,whfle revealing a modification in the design of the strip slot;

FIGURE 8 is a diagrammatic view of a method of, and apparatus for,cooling a polyphase travelling field magnetic separator core andwindings therefor according to the invention, being illustrated as asectional view;

FIGURE 9 is a perspective view of a modified polyphase travelling fieldmagnetic separator core construction according to the coolingarrangement illustrated in FIGURE 8;

FIGURE 10 is an illustration of a field shaping device according to theinvention associated with a magnetic separator core and a conveyor forthe material;

FIGURE 11 illustrates a preferred method of feeding material to apolyphase travelling field magnetic separator in conjunction with meansfor air cleaning the concentrate as it is obtained wherein the tailingsare disposed at a point considerably beyond the margins of the separatordevice;

FIGURE 12 is a sectional view of one preferred form of construction ofmagnetic separator according to the invention, illustrating the form ofhousing therefor whereby the device is sealed and may be partiallyimmersed in liquids if desired;

FIGURE 13 is an underside perspective view of the device of FIGURE 12;and

FIGURE 14 is a topside perspective view of the device of FIGURE 12;

Referring to the drawings and particularly FIGURE 1, the polyphasetravelling field magnetic separator core 10 having slots 11 carryingthree phase windings provides a travelling field moving in the directionof arrow Y which is adapted to carry magnetic material along the underface 12 in the direction of the arrow Z.

I designate that portion of the under surface or working face 12disposed over the feed conveyor, a pickup section or group of slots,which for a three phase winding,

3 may comprise at least six slots as indicated, or multiples of six. Inmany cases it is desirable to carry the material along the working face12 from a position above the feed conveyor to a point remote therefromat which the material may be discharged and accordingly I may designatea further group of slots as a transfer section or group. Finally, I maydesignate a final group of slots as a discharge section or group. Whiledevices of the prior art of the present class of magnetic separator havelaid stress upon the provision of a transfer section of a large numberof poles to provide the separation efliciency desired, I have found thatthe eficiency of separation is not materially controlled by any suchtransfer section but is mainly con trolled by the manner of picking upthe magnetic materials from the feeding device. This is a criticalconcept in determining what may be the controlling factor in thecapacity of apparatus of the present class.

In prior polyphase travelling field separators of the class consideredherein, a half slot three phase winding has been used. I have found thatthis affects the capacity of pickup since the end slots of the core areonly partially filled with windings resulting in a distorted flux at thepickup and discharge ends of the magnet. Thus, I may provide a full slotwinding at the pickup end by employing a type of winding for the core asillustrated in FIG- URE 2 for a three-phase power source and which maybe recognized as a type of chain winding. A feature in applying thisWinding to a core construction according to the invention is illustratedin FIGURE 2. wherein it will be apparent that the windings A, B and C instar connection, are arranged between the pole legs 13 in accordancewith a chain winding method but wherein the intermediate windings B arereversed for balance in a special manner according to the invention bymerely taking the connections 13b for the windings on one side of thecore construction carrying the poles 13, whereas the connections 13a and130 for the other two phases are at the other side of the coreconstruction as illustrated. This simple method of accomplishingreversing of the intermediate windings permits a facility of assemblyand servicing of considerable advantage in the overall design of theapparatus.

Referring to FIGURE 3, the last three coils 14, 15 and 1-6 such as thelast group of windings A, B and C of FIG- URE 2, may be controlled bythe control device of FIG- URE 3 to eifect a momentary limitation of thecurrent in said coil whereby the flux therein will be insuiiicient tohold magnetic material against the working face of the core of FIGURE 1in the discharge section of the separator. By reason of the heavycurrents involved in the development of high flux densities at linevoltages, I have found it undesirable to merely switch or sever thecurrent in this last winding section and according to the invention,provided the control device of FIGURE 3, supplied by a three phasesource of power wherein saturable reactors 14, and 16 having directcurrent windings 17, 18 and 19 respectively, control the amount ofcurrent in the last three coils or windings or in those coils orwindings comprising the discharge section of the device. In place ofsaturable reactors, I may use any other current modulating device suchas a saturable transformer, thyratron or ignition control device.

The direct current windings are preferably connected electrically inseries with a control variable resistance device 20 to a source ofdirect current as illustrated and including a switching device 21 inparallel with the resistance 20 whereby the direct current windingsnoted may be placed directly across the direct current source or inseries with the resistance 20. The resistance 24 should be of a valuebringing the impedance of each saturab-le reactor to a value greaterthan about three times the impedance of the discharge winding which itserves. In this way, the magnetic field in the discharge section will bebrought to a sufficiently low value that magnetic material will bereleased therefrom. On the other hand and 4- according to the invention,the maximum flux density in the core at the discharge section should beequal to or greater than the flux density in the transfer section ofFIG- URE l or if no transfer section is provided, then it should begreater than the flux density in the pickup section.

The switch 21 must be controlled in its time cycle and can only be openfor a short period of time; otherwise the material ready for transfer tothe discharge section will build up and cause a choking effect.Accordingly, the flux is reduced in the discharge section of the corefor a period of time between one-tenth of a second and one-half of asecond. Too short a period of time does not permit the magneticparticles to fall a suflicient distance to be free of the influence ofthe magnetic field of the discharge section. On the other hand, if thetime period at very low or negligible flux density is unnecessarilylong, the capacity of the device may be limited by a choking condition.The rate at which the discharge sec tion is covered by the material fromthe pickup section is the controlling factor and this is determined bythe size of the magnetic materials; a faster rate of covering beingexperienced with larger sized particles.

Therefore, with coarse magnetic materials, I may provide a dischargesection having twice the number of slots than serve in the pickupsection. Even when the discharge section has the same number of slots asthe pickup section, it is possible by limiting the discharge time toabout one-tenth of a second, to provide a capacity in the dischargesection equal to about of the capacity in the pickup section. This willinvolve a choking effect of about 5% of the magnetic materials. However,by increasing the field strength of the discharge sect-ion by a factorof about 5% the capacity of the discharge section can be brought up tothe capacity of the pickup section and this forms an important part ofthe present invention. It will be apparent that since the dischargesection will operate at a lesser duty cycle than the pickup section, thewinding may 'be the same design in both sections, within limitsappreciated by persons skilled in the art.

I provide a time cycle control for the discharge section in the mannerillustrated in FIGURES 4 and 5 wherein the pressure switch 21 which maybe of any suitable known construction having a switch arm 22 and beingof a normally closed class, is adapted to be opened by depressing thearm 22 above the line 23 as indicated. This may be accomplished byproviding an adjustable circular cam wheel 24 on shaft 25 adjustable ineccentricity by means of the screw 26 passing through the brackets 27 onthe cam and in threaded engagement in the threaded bore 23 of the shaft25. The shaft 25 is driven by a gear reduction device 29 driven by amotor 3%) controlled in speed by a variable transformer 31 connected toa suitable source of alternating current 32. The switch 21 is connectedin parallel with the resistor 20, the latter being in series with thedirect current windings of the saturable' reactor coils 17, 18 and 19 asindicated.

In operation, the cam wheel 24 traces a motion indicated in curve 33 inaccordance with the desired adjustment to actuate the switch 21 at amechanical switching level corresponding to the line 34 at which theswitch will be actuated to the open position for the period indicated bythe width of the valleys of the square wave 35 in the upper portion ofthe diagram but wherein the current in the direct current windingdecreases to the value as at 35. Observe that when switch 21 is closed,the current in direct current reactor windings is at the level 36 atwhich the flux density in the discharge section is a maximum. In thiswe. modulation of the current in the discharge windings is effected bycontrolling currents of small magnitude.

A general arrangement of overall control of the flux density of thevarious sections of the core of the separator is illustrated in FIGURE 6wherein the windings for the pickup, transfer and discharge sections aredesignated as groups 1, 2 and 3, respectively. The coil groups 1 and 2preferably are served by a three phase source of alternating current 37through a variable transformer 38 leaving the third group for thedischarge section to be served directly from the source of current 37,so that the flux density of groups 1 and 2 may be adjusted to a fluxdensity lower than the flux density of the discharge group, to avoidchoking. A feeding device 39 such as a magnetic vibrating feeder, isshown feeding magnetic material mixed with non-magnetic material to thefirst group at which the magnetic material 40 is picked up and thenonmagnetic material 41 falls into a tailings bin 42. As indicated atgroup 2, part of the magnetic material may fall away into a bin 4-3which material may be of a class H type of concentrate or a middling,wherein the magentic particles may have attached thereto, non-magneticmaterial. The purer concentrate proceeds to the discharge group 3 and isreleased therefrom in the manner previously explained to fall into thebin 44 to constitute a class I concentrate.

Where the group 2 section of the core serves as a part of group 1, thatis, it is effective in pickup of material from the feeder and isdisposed over the feeder, no middlings will be obtained and theresulting concentrating treatment will deliver a concentrate and atailing only. On the other hand, where the second group forms part ofthe discharge group, no middlings will be obtained and this is thepreferred manner of operating the device of the invention.

As is well known, the strength of the magnetic field need not be verygreat to pick up magnetic particles and with magnetic separators of thepresent class but of the prior art, a fiuX density in the core structureof about 2,500 gauss has been found satisfactory for picking up magneticmaterial providing the feeder is positioned close to the working face ofthe magnet. However, the capacity of such prior art core constructionsfor conveying the lifted material to the discharge end of the magnet, isseriously limited by the flux density in the magnet core.

It is undesirable with prior art methods to increase the liux density ofthe core above that sufiicient to pick up the desired magnetic materialfrom a feeder disposed closely to the surface of the pickup section ofthe core. However, according to the present invention, the pickup fieldstrength is controlled relative to the particles being lifted, not bylimiting the flux operated in the core construction, but by placing thematerial feeder a relatively large distance from the face of the pickupsection while providing a large flux density in the core construction todeliver a large handling capacity for the separator. In this way, adeeper bed of feed can be fed to the pickup section of the working faceof the separator core without the proximity of the working face of thecore seriously limiting the depth of feed thereto in relation to thecapacity of the device.

It will be apparent to skilled persons that the problem of providing ahigh flux density core construction of generally shallow rectangularform presents a problem of the worst sort in electrical design becausethe general core construction is of insufiicient depth to developpractical convection cooling by air. The laymon may visualize that withan open-ended core construction of the present type, the problemcorresponds substantially to the case of removing the rotor from aninduction motor and applying current to the stator windings. Under suchconditions, the stator would be limited to a flux density of probablyless than 2,000 gauss, with permissible temperature rises underconditions of natural cooling. YVhile very large core constructions maybe visualized wherein the centre to centre distance between poles is ofthe order of four inches or greater where natural air cooling may beemployed while developing flux densities in the core of a value near toor at the saturation point, it must be realized that such largestructures are accompanied by problems associated with the character ofa face-covering sheet and the structural support of the core againstbending.

Thus, referring to FIGURE 7, the core construction 45 comprised oflaminations 46 having poles 47 separated by winding openings 48terminating in pole spaces 49 separated by slots 50 and the working face51 thereof, is covered in its working face by a covering sheet ofmaterial 52, tensioned and fastened as by the screws 53.

The present invention therefore contemplates a sheet tensioning systemas hereinafter disclosed in more detail in respect to FIGURES 12 to 14,particularly practical for those sizes of core construction which mustnecessarily be cooled by some means to develop a reasonably high fluxdensity therein.

In the device of the present invention, a special cooling system isemployed as indicated in FIGURES 7 to 9 wherein windings 54 and 55 areplaced in the winding opening 43 in such manner as to leave an airpassage 56 therethrough, such windings being preferably held in place byopen structured retaining means 57 such as an undulated or corrugatedsheet of fibrous material. The whole assembly is held in Winding openingby means of a conventional form of fibre slot strip 58. If desired, amodified design of strip slot 59 may be employed, to which may befastened the sheet 53 by means of screws 60 at various points on theunderside of the core construction. I prefer, however, to leave theworking surface 51 of the core construction completely free ofobstruction and while the sheet 52 is shown as indented as at 61 toeffectively countersink the head 62 of screw 60, I prefer to avoid suchconstruction unless found to be essential over very large core surfaceswhere the sheet 52 may be discontinuous and may be comprised of a plurality of separate edge sealed sheets.

As will be evident from an examination of FIGURE 8, the core is built upfrom a plurality of laminated sections 63 which may be four in number,the sections being spaced by separators 64 in the form of rigid plateswelded thereto as indicated in FIGURE 9 along the pole legs whereby airor other cooling medium may be forced from manifolds 65 connecting to acommon source pipe 66 continuously into two of the longitudinal slots64a to follow a flow path as indicated by the flow line arrows. Thecooling medium passes directly over the surfaces of the windings to exitat the ends 67 of the overall construction and at the midslot exitsthereof as indicated. The spaces or slots between the sections receivinginlet cooling medium are commonly connected by some manifoldconstruction as indicated, the outlet slots and openings being free topermit the exhaust of the cooling medium to the inner confines of anysuitable housing (not shown) extending thereabout.

Observe that a continuous sheet 68 on the working face 69 seals thisworking face against escape of the cooling medium.

In FIGURE 9, a modification of the cooling arrangement is illustrated inthat the core construction is shown wherein the inlet cooling medium isbrought in by way of a common duct 69a into a manifold 70 of sheet metalfastened to the core pieces or sections 71 and 72 by means of suitablescrews 73 as shown. Arrow lines 74 indicate the manner of flow of thecooling medium from the centrally located ventilating slot 75 outwardlythrough the core construction.

As indicated in FIGURE 7, the ends of the core sections are all commonlywelded or otherwise joined to a supporting angle 76 whereby the completecore may be mounted in a suitable housing if desired. The laminations ofthe core are held in assembly by transverse seam welds as indicated inFIGURE 7 at 77 and 78, 360 electrical degrees apart along the uppersurface of the core above every seventh pole for the winding arrangementshown. The sides of the core are supported in the manner discussed inmore detail hereinafter with reference to FIG- URE 12.

Many experiments have shown that an undesirable ef fect arises infeeding material to the pickup section of a magnetic separator of thetype depicted in the prior art,

as will be evident from an examination of FIGURE 10, i1- lustrating animprovement according to the invention. A conveyor 80 such as avibrating feeder, if directed in the direction of material conveyed bythe working face 81 of core 82 as in the direction of the arrow Y mustforce the fed material against the end field pattern of the core 82, thecondition sometimes causing a choking of material at the point of pickupparticularly if the feeder is arranged to feed the material closely tosubstantially the first pole only of the core. I avoid this condition byany one of three methods which limit choking effects, or all of thesemethods combined as indicated in FIGURE 10. Thus, I may provide a sheet81 of a magnetic material such as a sheet material of core laminationsheet metal so that although the pole ends 83 may be substantiallysquare as indicated, with substantially square slots 84, the effectivepole end shape will be of a rounded nature in respect to the fieldpattern therefrom. In this way, a more uniform field is generated fromthe pole. Secondly, more particularly to avoid a field interferenceeffect with the feeding arrangement illustrated in FIGURE 10, the feeder80 is positioned at an angle with respect to the core so that themagnetizing force is very small as the fed material enters the fieldnear the first pole 83. It will be apparent hereinafter that I prefer inany case to incline a conveyor or feeder with respect to the workingface 81 for improving selectivity of pickup of material therefrom.Another method of controlling the effective field at the pickup end ofthe magnet when feeding in the direction of conveyance along the magnet,involves a field shaping device 85 built up of laminations of the samematerial from which the core 82 is made. The field shaping pole piece 85may be of a length less than the pickup section of the core to shape thefield mainly at the first pole of the pickup section.

I have discovered that I may provide an optimum feed capacity to aseparator device of the class described herein while avoiding choking atall rates of feed and While feeding material to a substantial depth onthe conveyor by feeding material to the separator in the oppositedirection from that used heretofore.

As indicated in FIGURE 11, a magnetic separator of the travelling fieldclass designated by numeral 86 may be positioned over a feeder conveyorbelt 87 so that the belt moves in a direction under the separator fromthe discharge end 87a thereof to pickup end 88 thereof. A concentratebelt 89 is disposed transversely of the separator 86 and the feeder belt87 to carry away concentrate dropped in the direction of the arrows 90from the discharge end of the separator. The material on the conveyor 87is drawn toward the working face 91 at an increasing attractive force asthe material is moved closer to the pickup end 88. A bed of material maybe fed on the belt 87 so that the bed is agitated by the increasingmagnetic field as the material proceeds below the separator. Thus thewhole undersurface of the separator is effective as a combined pickupand transferring section, with the exception of the discharge section87a.

Observe that the conveyor 87 projects beyond the marginal edges of theseparator 86 to a tailings discharge point 92 positioned a substantialdistance from the separator and adapted to discharge tailings into asuitable bin 93.

An air cleaning system 94 may be employed in conjunction with thetailings discharge bin such as a bagging machine 95 or cyclone separatoras may be preferred, operative by an air fan 96 and associated with anair enclosure or housing 97 extending over the feed belt 87 and theseparator up to the discharge section 87a thereof and the concentrateconveyor 89. In this way, a feature of the invention is provided in areverse draft or counter-current air system in the region of the pickupof magnetic material from the conveyor 87 whereby the concentrate is airscoured during pickup and the whole operation may be maintainedeffectively dustless.

In FIGURES 12 to 14 I show a preferred form of housing construction fora magnetic separator according to this invention embodying automatictensioning means for the cover sheet of the working face thereof andadapted to entirely seal the separator from dust and permit the workingface of the separator to be submerged in a liquid for wet separationpractice, if desired.

In FIGURE 1 2, the housing 98 is shown comprised of two main parts: atop cover 99 or body part and an under cover or closure part 100. Whilea cast metal construction is illustrated, a built-up form ofconstruction may be employed, if desired. The separator core 101 isillustrated in chain lines, being supported by transversely extendingangle members 102 extending outwardly to be fastened to the body 99 bymeans of eye bolts 103 passing therethrough and extending upwardlybeyond the body to present loops 104 adapted to be connected to cablesor to be rigidly fastened to suitable framing, as may be desired. Asreviewed in respect to the construction of FIGURES 7 and 9, thetransverse angle member 102 connects to the core 101 and transverselysupports the latter against bending due to its weight. Lengthwisebending of the core may be provided against by the longitudinallyextended angles 105 Welded to the side edges of the core to the face 106thereof. The angles 105 have welded thereto on the outer surfaces of theupright legs thereof, tooth supports 105a in the form of rigid platessimilar to the core spacers 64 of FIGURE 9 but of greater height forsecurement to the angle 1G5 and acting to retain the leg or toothportions of the core in compressive assembly.

As indicated in FIGURES 13 and 14, an air inlet pipe 107 commuicateswith manifold 108 to the core 101, the exhaust of from the core flowinginto the confines of the housing and escaping from the outlet 109. In athree phase type of core, chain wound as set forth herein, connectionfor two phases may be made by cables 110 and 111 on one side of the coreand the connection for the intermediate reverse windings such as by thecable 112 on the other side of the core. These cables, along with othercables for the discharge windings, are brought to a connection box 113and through a main cable 114 to suitable controlling transformers andthe three phase source of power.

A feature of the invention resides in the provision of an undercover 100having an opening 115 extending freely about the marginal edges of theseparator core and carrying a cover sheet 116 fastened thereto,preferably by machine screws 116a. The bolts 103, as before mentioned,support the core by the angle 102 by means of the nuts 117 suspendingthe apparatus free for servicing. The cover 100 is placed over theexposed parts of the apparatus the edges 118 thereof cooperating withsealing edges 119 of the top cover to form a seal in conjunction withthe resilient rubber gasket 120. The undercover is held in place bymeans of strong springs 121, compressed by means of the nuts 122 on thelower extending portions of the bolts 103, a dust seal being effected bymeans of the compressible washer 123 of rubber or other suitablematerial. 7

Accordingly, as the pressure of springs 121 is increased by tighteningthe nuts '122, the tension in the sheet 116 will increase. So long asthe stresses in the sheet 116 are set to values less than the elasticlimits of the material, tensioning of the sheet 116 over the under face117 of the core by engagement therewith, will permit compensation forthermal expansion of the sheet 116 within a limited range oftemperature.

Prior apparatus of the present class being capable of handling smallparticle sizes only, necessitated the overgrinding of many ores. I havefound that the larger the interpole distances (centre to centre ofadjacent poles), the larger the diameter of particle which may behandled, pnoviding "a suflicient flux density is available. Moreover,larger particle sizes move at greater speed along the working face ofthe separator core, thus permitting much greater capacities with coreconstructions of the invention having much larger interpole spacing thanheretofore contemplated, and having directly cooled windings enablinghigh flux density to be developed.

In accordance with this concept, the capacity of the present class ofseparator may be increased to as much as ten times the capacityavailable heretofore. The novel method of inclining the material feederrelative to the working face of the present class of separator frees thepresent method of separation from capacity limitations formerly imposedby other methods. The method of providing an increasing strength offield from the pickup section of the separator to the discharge sectionthereof by operating the latter at higher flux density avoids capacitylimitations derived from choking effects.

Thus, one may prepare a material by grinding to optimum size, i.e., to asize only sufiiciently small to liberate the desired purity of magneticparticle after which the prepared material is fed to the separator at anangle with respect to the working face thereof as set forth.

According to the invention, 1 provide apparatus for magneticallyconcentrating such material including the separator core structure andrelated devices. The invention also relates to the method ofmagnetically concentrating such material wherein the material is movedin the ways described toward a sheet along which a travelhng magneticfield moves and through which such field extends toward said material.

I claim:

1. Magnetic material concentrating apparatus, compris- (a) a corestructure having a working face,

(b) means connectable with a source of electrical power for generating atravelling magnetic field along said working face in a predetermineddirection, and

(c) means for moving material at an angle toward sald working face, in adirection the same as the direction of travel of said magnetic fieldtherealong and along a path of substantially greater length than adimension of said working face.

2. Magnetic material concentrating apparatus compris- (a) a corestructure having a working face,

(b) means connectable with a source of electrical power for generating atravelling magnetic field along said working face in a predetermineddirection,

(c) means for feeding material to said wor g face in 'a direction thesame as the direction of travel of said magnetic field therealong, and

(d) means for moving a current of air ad acent 831d working face in adirection substantially opposed to the direction of motion of magneticparticles along Said Working face, thereby effectively removingnonmagnetic particles entrapped within said magnetic particles.

3. Magnetic material concentrating apparatus, compr1s- (a) a corestructure having a working face,

(b) means connectable with a source of electrical power for generating atravelling magnetic field along said working face in a predetermineddirection,

(0) means for moving material at an angle toward said working face, in adirection the same as the direction of travel of said magnetic fieldtherealong and along a path of substantially greater length than adimension of said working face, and

(d) means for moving air adjacent said working face in a directionsubstantially opposed to the direction of motion of magnetic particlestherealong, thereby removing non-magnetic particles entrapped withinsaid magnetic particles.

4. Magnetic material concentrating apparatus, com prising:

(a) a core structure having a working face,

(17) means connectable with a source of electrical 10 power forgenerating a travelling magnetic field along said working face in apredetermined direction,

(0) means for conveying material at an angle toward said Working face,in a direction the same as the direction of travel of said magneticfield therealong and along a path of substantially greater length than adimension of said working face,

(a?) means for moving air adjacent said working face in a directionsubstantially opposed to the direction of motion of magnetic particlestherea-long, thereby to remove non-magnetic particles entrapped withinsaid magnetic particles, and

(e) means supporting said core structure to dispose the working facethereof over said conveying means between the ends of said path and atan angle with respect thereto so that the material thereon moves closerto said face as it is conveyed along said path, said path projectingbeyond said working face a distance sufiicient to remove said materialto a position outside the influence of said magnetic field.

5. Magnetic material concentrating apparatus, comprising:

(a) a core structure having a working face,

(b) means connectable with a source of electrical power for generating atravelling magnetic field along said working face in a predetermineddirection,

(0) means for conveying material at an angle toward said working face,in a direction the same as the direction of travel of said magneticfield therealong andalong a path of substantially greater length than adimension of said working face, and

(d) means supporting said core structure to dispose the working facethereof over said conveying means between the ends of said path and atan angle with respect thereto so that the material thereon moves closerto said face as it is conveyed along said path, said path projectingbeyond said working face a distance sufficient to remove said materialto a position outside the influence of said magnetic field.

6. Magnetic material concentrating apparatus compris- (a) a corestructure having a working face,

(b) means connectable with a source of electrical power for generating atravelling magnetic field along said working face in a predetermineddirection,

(c) means for conveying material to said working face in a direction thesame as the direction of travel of said magnetic field therealong,

(0?) means for moving a current of air adjacent said working face in adirection substantially opposed to the direction of motion of magneticparticles along said working face, thereby effectively removingnonmagnetic particles entrapped within said magnetic particles, and

(e) means supporting said core structure to dispose the working facethereof over said conveying means between the ends of said path and atan angle with respect thereto so that the material thereon moves closerto said face as it is conveyed along said path, said path projectingbeyond said working face a distance suflicient to remove said materialto a position outside the influence of said magnetic field.

7. The magnetic material concentrating apparatus as claimed in claim 1including:

(d) control means for effecting a momentary limitation of the current inthe discharge section of said working face whereby the flux will beinsuflicient to hold magnetic material against said working face in saidsection.

8. The magnetic material concentrating apparatus as claimed in claim 2including:

(e) control means for effecting a momentary limitation of the current inthe discharge section of said working face whereby the flux will beinsufiicient to hold magnetic material against said working face in saidsection.

9. The magnetic material concentrating apparatus as claimed in claim 3including:

(e) control means for eifecting a momentary limitation of the current inthe discharge section of said working face whereby the flux will beinsufficient to hold magnetic material against said working face in saidsection.

10. The magnetic material concentrating apparatus as claimed in claim 4including:

(1) control means for effecting a momentary limitation of the current inthe discharge section of said working face whereby the flux will beinsufiicient to hold magnetic material against said Working fiace insaid section.

11. The magnetic material concentrating apparatus as claimed in claim 5including:

(e) control means for effecting a momentary limitation of the current inthe discharge section of said Working face whereby the flux will beinsufficient to hold magnetic material against said working face in saidsection.

12. The magnetic material concentrating apparatus as claimed in claim 6including:

(1) control means for effecting a momentary limitation of the current inthe discharge section of said Working face whereby the flux will beinsuflicient to hold magnetic material against said Working face in saidsection.

13. The magnetic material concentrating apparatus as claimed in claim 7including:

(2) time cycle control means in association with said control means andadapted, in conjunction with said control means, to efiect saidmomentary limitation of current at a predetermined interval and for alength of time dependent upon the size of material being processed.

14. The magnetic material concentrating apparatus as claimed in claim 8including:

(7) time cycle control means in association with said control means andadapted, in conjunction with said control means, to effect saidmomentary limitation of current at a predetermined interval and for alength of time dependent upon the size of material being processed.

15. The magnetic material concentrating apparatus as claimed in claim 9including:

(f) time cycle control means in association with said control means andadapted, in conjunction with said control means, to effect saidmomentary limitation 12 of current at a predetermined interval and for alength of time dependent upon the size of material being processed.

16. The magnetic material concentrating apparatus as claimed in claim 10including:

(g) time cycle control means in association with said control means andadapted, in conjunction with said control means, to effect saidmomentary limitation of current at a predetermined interval and for alength of time dependent upon the size of material 7 being processed.

17. The magnetic material concentrating apparatus as claimed in claim 11including:

(f) time cycle control means in association with said control means andadapted, in conjunction with said control means, to eflect saidmomentary limitation of current at a predetermined interval and for alength of time dependent upon the size of material being processed.

18. The magnetic material concentrating apparatus as claimed in claim 12including:

(g) time cycle control means in association with said control means andadapted, in conjunction with said control means, to effect saidmomentary limitation of current at a predetermined interval and for alength of time dependent upon the size of material being processed. 1

References Cited in the file of this patent OTHER REFERENCES Three PhaseA.C. Can Improve Fine Size Magnetic Separation, by Suen Eketorp,Engineering and Mining Journal, vol 152, Issue 10, October 1951, pages82, 83, 118.

1. MAGNETIC MATERIAL CONCENTRATING APPARATUS, COMPRISING: (A) A CORESTRUCTURE HAVING A WORKING FACE, (B) MEANS CONNECTABLE WITH A SOURCE OFELECTRICAL POWER FOR GENERATING A TRAVELLING MAGNETIC FIELD ALONG SAIDWORKING FACE IN A PREDETERMINED DIRECTION, AND (C) MEANS FOR MOVINGMATERIAL AT AN ANGLE TOWARD SAID WORKING FACE, IN A DIRECTION THE SAMEAS THE DIRECTION OF TRAVEL OF SAID MAGNETIC FIELD THEREALONG AND ALONG APATH OF SUBSTANTIALLY GREATER LENGTH THAN A DIMENSION OF SAID WORKINGFACE.